Memory B cells targeting SARS-CoV-2 spike protein and their dependence on CD4+ T cell help

Immunogenicity and safety study of a single dose of SpikoGen® vaccine as a heterologous or homologous intramuscular booster following a primary course of mRNA, adenoviral vector or recombinant protein COVID-19 vaccine in ambulatory adults

BACKGROUND

SpikoGen® is a subunit recombinant Wuhan spike protein produced in insect cells and formulated with Advax-CpG55.2™ adjuvant. It is approved for adult and pediatric use in the Middle East. This study tested the safety and immunogenicity of SpikoGen® as a 3rd, 4th or 5th dose booster following a primary immunisation course of mRNA, adenovirus or SpikoGen® vaccine.

METHODS

The trial recruited participants who had received a previous doses of COVID-19 vaccine more than 3 months prior. Each received a single intramuscular booster dose of SpikoGen® vaccine. Spike and nuclear protein antibody levels were measured at 1 and 3 months post-booster, together with collection of data on SARS-CoV-2 breakthrough infections and symptoms of long COVID.

RESULTS

One-month post-booster, anti-spike IgG, sVNT, and pVNT levels were increased in all groups and there was ∼4-fold neutralizing antibodies against the heterologous Omicron BA.2 and BA.4/5 strains. The SpikoGen®-prime group had the highest levels of anti-spike IgG3, consistent with the Advax-CpG adjuvant driving IgG3 induction. There was no effect of age on the vaccine response. The booster dose was well tolerated with no vaccine-associated serious adverse events. Nine participants (9/74, 12.2 %) had a breakthrough SARS-CoV-2 infection between 2 weeks and 3 months post-booster. No long COVID was observed after breakthrough infections. Breakthrough infection was negatively correlated with baseline anti-nuclear protein IgG seropositivity.

CONCLUSION

A single SpikoGen® booster was well tolerated and stimulated cross- antibody responses against Omicron variants, regardless of the primary vaccine course received. With SARS-CoV-2 variants continuing to evolve, ongoing research is needed into optimum booster strategies.

CLINICALTRIALS

gov registration. NCT05542862.

Deep profiling of B cells responding to various pathogens uncovers compartments in IgG memory B cell and antibody-secreting lineages

Improving our understanding of B cell transition to memory B cells (MBCs) and antibody-secreting cells (ASCs) is crucial for clinical monitoring and vaccine strategies. To explore these dynamics, we compared prepandemic antigen responses (influenza hemagglutinin, respiratory syncytial virus fusion glycoprotein, and tetanus toxoid) with recently encountered severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigen responses in convalescent COVID-19 patients using spectral flow cytometry. Our analysis revealed the CD43+CD71+IgG+ activated B cell subset, highly enriched for SARS-CoV-2 specificities, as a juncture for ASC and MBC differentiation, with CD86+ phenotypically similar to ASCs and CD86- to IgG+ MBCs. Moreover, subpopulations within IgG+ MBCs were further identified based on CD73 and CD24 expression. Activated MBCs (CD73-/CD24lo) were predominantly SARS-CoV-2-specific, while resting MBCs (CD73+/CD24hi) recognized prepandemic antigens. A CD95- subcluster within resting MBCs accounted for over 40% of prepandemic-specific cells, indicating long-lasting memory. These findings advance our understanding of IgG+ MBC and ASC development stages, shedding light on the decision-making process guiding their differentiation.

Immunologic and inflammatory consequences of SARS-CoV-2 infection and its implications in renal disease

The emergence of the COVID-19 pandemic made it critical to understand the immune and inflammatory responses to the SARS-CoV-2 virus. It became increasingly recognized that the immune response was a key mediator of illness severity and that its mechanisms needed to be better understood. Early infection of both tissue and immune cells, such as macrophages, leading to pyroptosis-mediated inflammasome production in an organ system critical for systemic oxygenation likely plays a central role in the morbidity wrought by SARS-CoV-2. Delayed transcription of Type I and Type III interferons by SARS-CoV-2 may lead to early disinhibition of viral replication. Cytokines such as interleukin-1 (IL-1), IL-6, IL-12, and tumor necrosis factor α (TNFα), some of which may be produced through mechanisms involving nuclear factor kappa B (NF-κB), likely contribute to the hyperinflammatory state in patients with severe COVID-19. Lymphopenia, more apparent among natural killer (NK) cells, CD8+ T-cells, and B-cells, can contribute to disease severity and may reflect direct cytopathic effects of SARS-CoV-2 or end-organ sequestration. Direct infection and immune activation of endothelial cells by SARS-CoV-2 may be a critical mechanism through which end-organ systems are impacted. In this context, endovascular neutrophil extracellular trap (NET) formation and microthrombi development can be seen in the lungs and other critical organs throughout the body, such as the heart, gut, and brain. The kidney may be among the most impacted extrapulmonary organ by SARS-CoV-2 infection owing to a high concentration of ACE2 and exposure to systemic SARS-CoV-2. In the kidney, acute tubular injury, early myofibroblast activation, and collapsing glomerulopathy in select populations likely account for COVID-19-related AKI and CKD development. The development of COVID-19-associated nephropathy (COVAN), in particular, may be mediated through IL-6 and signal transducer and activator of transcription 3 (STAT3) signaling, suggesting a direct connection between the COVID-19-related immune response and the development of chronic disease. Chronic manifestations of COVID-19 also include systemic conditions like Multisystem Inflammatory Syndrome in Children (MIS-C) and Adults (MIS-A) and post-acute sequelae of COVID-19 (PASC), which may reflect a spectrum of clinical presentations of persistent immune dysregulation. The lessons learned and those undergoing continued study likely have broad implications for understanding viral infections' immunologic and inflammatory consequences beyond coronaviruses.

Profile of Humoral Immunity and B Cell Pool in Infection with the SARS-CoV-2 Prototype Strain and AZD1222 (ChAdOx nCoV-19) Vaccination

BACKGROUND/OBJECTIVES

Understanding the behavior of B cells during infection and vaccination is important for determining protective humoral immunity. We evaluated the profile of humoral immunity and B cell pool in individuals who were acutely infected with SARS-CoV-2, recovered from COVID-19, or received two doses of the AZD1222 vaccine.

METHODS

Peripheral blood mononuclear cells (PBMCs) from these individuals were subjected to in vitro stimulation to promote the differentiation of B cells into antibody-secreting cells (ASCs), and the ELISpot evaluated the abundance of pan and SARS-CoV-2 Spike S1-reactive IgG+ ASC. Stimulated PBMCs were characterized using flow cytometry. Culture supernatants were assessed for soluble B-cell-activating factors. The IgA and IgG for the S1 were evaluated through ELISA.

RESULTS

The recovered individuals displayed a robust S1 ASC compared to acute and vaccinated individuals. Although the frequency of total B cells or B cell subsets did not vary among the groups, plasmablast cells were increased in naïve and double-negative B cells in the acute, recovered, and vaccinated individuals. Similar IgA and IgG production appeared to be present in the acute and recovered individuals. During vaccination, more IgG is produced than IgA. In acute patients, BAFF levels were positively correlated with total B cells and IgG+ plasmablast cells but negatively correlated with IgA+ plasmablast cells.

CONCLUSIONS

Vaccination and natural infection with COVID-19 induce a differential profile and functionality of B cells. We suggest that new vaccines against COVID-19 incorporate molecular adjuvants that regulate B lymphocyte functionality and consider the beneficial aspects of the IgA response in addition to IgG.

Heterologous booster vaccination enhances antibody responses to SARS-CoV-2 by improving Tfh function and increasing B-cell clonotype SHM frequency

Heterologous prime-boost has broken the protective immune response bottleneck of the COVID-19 vaccines. however, the underlying mechanisms have not been fully elucidated. Here, we investigated antibody responses and explored the response of germinal center (GC) to priming with inactivated vaccines and boosting with heterologous adenoviral-vectored vaccines or homologous inactivated vaccines in mice. Antibody responses were dramatically enhanced by both boosting regimens. Heterologous immunization induced more robust GC activation, characterized by increased Tfh cell populations and enhanced helper function. Additionally, increased B-cell activation and antibody production were observed in a heterologous regimen. Libra-seq was used to compare the differences of S1-, S2- and NTD-specific B cells between homologous and heterologous vaccination, respectively. S2-specific CD19+ B cells presented increased somatic hypermutations (SHMs), which were mainly enriched in plasma cells. Moreover, a heterologous booster dose promoted the clonal expansion of B cells specific to S2 and NTD regions. In conclusion, the functional role of Tfh and B cells following SARS-CoV-2 heterologous vaccination may be important for modulating antibody responses. These findings provide new insights for the development of SARS-CoV-2 vaccines that induce more robust antibody response.

Longitudinal dynamic single-cell mass cytometry analysis of peripheral blood mononuclear cells in COVID-19 patients within 6 months after viral RNA clearance

This study investigates the longitudinal dynamic changes in immune cells in COVID-19 patients over an extended period after recovery, as well as the interplay between immune cells and antibodies. Leveraging single-cell mass spectrometry, we selected six COVID-19 patients and four healthy controls, dissecting the evolving landscape within six months post-viral RNA clearance, alongside the levels of anti-spike protein antibodies. The T cell immunophenotype ascertained via single-cell mass spectrometry underwent validation through flow cytometry in 37 samples. Our findings illuminate that CD8 + T cells, gamma-delta (gd) T cells, and NK cells witnessed an increase, in contrast to the reduction observed in monocytes, B cells, and double-negative T (DNT) cells over time. The proportion of monocytes remained significantly elevated in COVID-19 patients compared to controls even after six-month. Subpopulation-wise, an upsurge manifested within various T effector memory subsets, CD45RA + T effector memory, gdT, and NK cells, whereas declines marked the populations of DNT, naive and memory B cells, and classical as well as non-classical monocytes. Noteworthy associations surfaced between DNT, gdT, CD4 + T, NK cells, and the anti-S antibody titer. This study reveals the changes in peripheral blood mononuclear cells of COVID-19 patients within 6 months after viral RNA clearance and sheds light on the interactions between immune cells and antibodies. The findings from this research contribute to a better understanding of immune transformations during the recovery from COVID-19 and offer guidance for protective measures against reinfection in the context of viral variants.

To be remembered: B cell memory response against SARS-CoV-2 and its variants in vaccinated and unvaccinated individuals

COVID-19 disease has plagued the world economy and affected the overall well-being and life of most of the people. Natural infection as well as vaccination leads to the development of an immune response against the pathogen. This involves the production of antibodies, which can neutralize the virus during future challenges. In addition, the development of cellular immune memory with memory B and T cells provides long-lasting protection. The longevity of the immune response has been a subject of intensive research in this field. The extent of immunity conferred by different forms of vaccination or natural infections remained debatable for long. Hence, understanding the effectiveness of these responses among different groups of people can assist government organizations in making informed policy decisions. In this article, based on the publicly available data, we have reviewed the memory response generated by some of the vaccines against SARS-CoV-2 and its variants, particularly B cell memory in different groups of individuals.

Booster vaccination is required to elicit and maintain COVID-19 vaccine-induced immunity in SIV-infected macaques

ABSTRACTProlonged infection and possible evolution of SARS-CoV-2 in patients living with uncontrolled HIV-1 infection highlight the importance of an effective vaccination regimen, yet the immunogenicity of COVID-19 vaccines and predictive immune biomarkers have not been well investigated. Herein, we report that the magnitude and persistence of antibody and cell-mediated immunity (CMI) elicited by an Ad5-vectored COVID-19 vaccine are impaired in SIV-infected macaques with high viral loads (> 10⁵ genome copies per ml plasma, SIV^hi) but not in macaques with low viral loads (< 10⁵, SIV^low). After a second vaccination, the immune responses are robustly enhanced in all uninfected and SIV^low macaques. These responses also show a moderate increase in 70% SIV^hi macaques but decline sharply soon after. Further analysis reveals that decreased antibody and CMI responses are associated with reduced circulating follicular helper T cell (TFH) counts and aberrant CD4/CD8 ratios, respectively, indicating that dysregulation of CD4⁺ T cells by SIV infection impairs the COVID-19 vaccine-induced immunity. Ad5-vectored COVID-19 vaccine shows no impact on SIV loads or SIV-specific CMI responses. Our study underscores the necessity of frequent booster vaccinations in HIV-infected patients and provides indicative biomarkers for predicting vaccination effectiveness in these patients.

Immune imprinting and next-generation coronavirus vaccines

Vaccines based on historical virus isolates provide limited protection from continuously evolving RNA viruses, such as influenza viruses or coronaviruses, which occasionally spill over between animals and humans. Despite repeated booster immunizations, population-wide declines in the neutralization of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants have occurred. This has been compared to seasonal influenza vaccinations in humans, where the breadth of immune responses induced by repeat exposures to antigenically distinct influenza viruses is confounded by pre-existing immunity-a mechanism known as imprinting. Since its emergence, SARS-CoV-2 has evolved in a population with partial immunity, acquired by infection, vaccination or both. Here we critically examine the evidence for and against immune imprinting in host humoral responses to SARS-CoV-2 and its implications for coronavirus disease 2019 (COVID-19) booster vaccine programmes.

Regulatory T cell-like response to SARS-CoV-2 in Jamaican fruit bats (Artibeus jamaicensis) transduced with human ACE2

Insectivorous Old World horseshoe bats (Rhinolophus spp.) are the likely source of the ancestral SARS-CoV-2 prior to its spillover into humans and causing the COVID-19 pandemic. Natural coronavirus infections of bats appear to be principally confined to the intestines, suggesting fecal-oral transmission; however, little is known about the biology of SARS-related coronaviruses in bats. Previous experimental challenges of Egyptian fruit bats (Rousettus aegyptiacus) resulted in limited infection restricted to the respiratory tract, whereas insectivorous North American big brown bats (Eptesicus fuscus) showed no evidence of infection. In the present study, we challenged Jamaican fruit bats (Artibeus jamaicensis) with SARS-CoV-2 to determine their susceptibility. Infection was confined to the intestine for only a few days with prominent viral nucleocapsid antigen in epithelial cells, and mononuclear cells of the lamina propria and Peyer's patches, but with no evidence of infection of other tissues; none of the bats showed visible signs of disease or seroconverted. Expression levels of ACE2 were low in the lungs, which may account for the lack of pulmonary infection. Bats were then intranasally inoculated with a replication-defective adenovirus encoding human ACE2 and 5 days later challenged with SARS-CoV-2. Viral antigen was prominent in lungs for up to 14 days, with loss of pulmonary cellularity during this time; however, the bats did not exhibit weight loss or visible signs of disease. From day 7, bats had low to moderate IgG antibody titers to spike protein by ELISA, and one bat on day 10 had low-titer neutralizing antibodies. CD4+ helper T cells became activated upon ex vivo recall stimulation with SARS-CoV-2 nucleocapsid peptide library and exhibited elevated mRNA expression of the regulatory T cell cytokines interleukin-10 and transforming growth factor-β, which may have limited inflammatory pathology. Collectively, these data show that Jamaican fruit bats are poorly susceptible to SARS-CoV-2 but that expression of human ACE2 in their lungs leads to robust infection and an adaptive immune response with low-titer antibodies and a regulatory T cell-like response that may explain the lack of prominent inflammation in the lungs. This model will allow for insight of how SARS-CoV-2 infects bats and how bat innate and adaptive immune responses engage the virus without overt clinical disease.

The role of interleukin-21 in COVID-19 vaccine-induced B cell-mediated immune responses in patients with kidney disease and kidney transplant recipients

T-cell-mediated help to B cells is required for the development of humoral responses, in which the cytokine interleukin (IL)-21 is key. Here, we studied the mRNA-1273 vaccine-induced SARS-CoV-2-specific memory T-cell IL-21 response, memory B cell response, and immunoglobulin (Ig)G antibody levels in peripheral blood at 28 days after the second vaccination by ELISpot and the fluorescent bead-based multiplex immunoassay, respectively. We included 40 patients with chronic kidney disease (CKD), 34 patients on dialysis, 63 kidney transplant recipients (KTR), and 47 controls. We found that KTR, but not patients with CKD and those receiving dialysis, showed a significantly lower number of SARS-CoV-2-specific IL-21 producing T cells than controls (P < .001). KTR and patients with CKD showed lower numbers of SARS-CoV-2-specific IgG-producing memory B cells when compared with controls (P < .001 and P = .01, respectively). The T-cell IL-21 response was positively associated with the SARS-CoV-2-specific B cell response and the SARS-CoV-2 spike S1-specific IgG antibody levels (both Pearson r = 0.5; P < .001). In addition, SARS-CoV-2-specific B cell responses were shown to be IL-21 dependent. Taken together, we show that IL-21 signaling is important in eliciting robust B cell-mediated immune responses in patients with kidney disease and KTR.

Infection pre-Ad26.COV2.S-vaccination primes greater class switching and reduced CXCR5 expression by SARS-CoV-2-specific memory B cells

Neutralizing antibodies strongly correlate with protection for COVID-19 vaccines, but the corresponding memory B cells that form to protect against future infection are relatively understudied. Here we examine the effect of prior SARS-CoV-2 infection on the magnitude and phenotype of the memory B cell response to single dose Johnson and Johnson (Ad26.COV2.S) vaccination in South African health care workers. Participants were either naïve to SARS-CoV-2 or had been infected before vaccination. SARS-CoV-2-specific memory B-cells expand in response to Ad26.COV2.S and are maintained for the study duration (84 days) in all individuals. However, prior infection is associated with a greater frequency of these cells, a significant reduction in expression of the germinal center chemokine receptor CXCR5, and increased class switching. These B cell features correlated with neutralization and antibody-dependent cytotoxicity (ADCC) activity, and with the frequency of SARS-CoV-2 specific circulating T follicular helper cells (cTfh). Vaccination-induced effective neutralization of the D614G variant in both infected and naïve participants but boosted neutralizing antibodies against the Beta and Omicron variants only in participants with prior infection. In addition, the SARS-CoV-2 specific CD8+ T cell response correlated with increased memory B cell expression of the lung-homing receptor CXCR3, which was sustained in the previously infected group. Finally, although vaccination achieved equivalent B cell activation regardless of infection history, it was negatively impacted by age. These data show that phenotyping the response to vaccination can provide insight into the impact of prior infection on memory B cell homing, CSM, cTfh, and neutralization activity. These data can provide early signals to inform studies of vaccine boosting, durability, and co-morbidities.

The role of immune activation and antigen persistence in acute and long COVID

In late 2019, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) triggered the global coronavirus disease 2019 (COVID-19) pandemic. Although most infections cause a self-limited syndrome comparable to other upper respiratory viral pathogens, a portion of individuals develop severe illness leading to substantial morbidity and mortality. Furthermore, an estimated 10%-20% of SARS-CoV-2 infections are followed by post-acute sequelae of COVID-19 (PASC), or long COVID. Long COVID is associated with a wide variety of clinical manifestations including cardiopulmonary complications, persistent fatigue, and neurocognitive dysfunction. Severe acute COVID-19 is associated with hyperactivation and increased inflammation, which may be an underlying cause of long COVID in a subset of individuals. However, the immunologic mechanisms driving long COVID development are still under investigation. Early in the pandemic, our group and others observed immune dysregulation persisted into convalescence after acute COVID-19. We subsequently observed persistent immune dysregulation in a cohort of individuals experiencing long COVID. We demonstrated increased SARS-CoV-2-specific CD4+ and CD8+ T-cell responses and antibody affinity in patients experiencing long COVID symptoms. These data suggest a portion of long COVID symptoms may be due to chronic immune activation and the presence of persistent SARS-CoV-2 antigen. This review summarizes the COVID-19 literature to date detailing acute COVID-19 and convalescence and how these observations relate to the development of long COVID. In addition, we discuss recent findings in support of persistent antigen and the evidence that this phenomenon contributes to local and systemic inflammation and the heterogeneous nature of clinical manifestations seen in long COVID.

Regulatory T Cell-like Response to SARS-CoV-2 in Jamaican Fruit Bats ( Artibeus jamaicensis ) Transduced with Human ACE2

Insectivorous Old World horseshoe bats ( Rhinolophus spp.) are the likely source of the ancestral SARS-CoV-2 prior to its spillover into humans and causing the COVID-19 pandemic. Natural coronavirus infections of bats appear to be principally confined to the intestines, suggesting fecal-oral transmission; however, little is known about the biology of SARS-related coronaviruses in bats. Previous experimental challenges of Egyptian fruit bats ( Rousettus aegyptiacus ) resulted in limited infection restricted to the respiratory tract, whereas insectivorous North American big brown bats ( Eptesicus fuscus ) showed no evidence of infection. In the present study, we challenged Jamaican fruit bats ( Artibeus jamaicensis ) with SARS-CoV-2 to determine their susceptibility. Infection was confined to the intestine for only a few days with prominent viral nucleocapsid antigen in epithelial cells, and mononuclear cells of the lamina propria and Peyer's patches, but with no evidence of infection of other tissues; none of the bats showed visible signs of disease or seroconverted. Expression levels of ACE2 were low in the lungs, which may account for the lack of pulmonary infection. Bats were then intranasally inoculated with a replication-defective adenovirus encoding human ACE2 and 5 days later challenged with SARS-CoV-2. Viral antigen was prominent in lungs for up to 14 days, with loss of pulmonary cellularity during this time; however, the bats did not exhibit weight loss or visible signs of disease. From day 7, bats had low to moderate IgG antibody titers to spike protein by ELISA, and one bat on day 10 had low-titer neutralizing antibodies. CD4 + helper T cells became activated upon ex vivo recall stimulation with SARS-CoV-2 nucleocapsid peptide library and exhibited elevated mRNA expression of the regulatory T cell cytokines interleukin-10 and transforming growth factor-β, which may have limited inflammatory pathology. Collectively, these data show that Jamaican fruit bats are poorly susceptibility to SARS-CoV-2 but that expression of human ACE2 in their lungs leads to robust infection and an adaptive immune response with low-titer antibodies and a regulatory T cell-like response that may explain the lack of prominent inflammation in the lungs. This model will allow for insight of how SARS-CoV-2 infects bats and how bat innate and adaptive immune responses engage the virus without overt clinical disease.

Author Summary

Bats are reservoir hosts of many viruses that infect humans, yet little is known about how they host these viruses, principally because of a lack of relevant and susceptible bat experimental infection models. Although SARS-CoV-2 originated in bats, no robust infection models of bats have been established. We determined that Jamaican fruit bats are poorly susceptible to SARS-CoV-2; however, their lungs can be transduced with human ACE2, which renders them susceptible to SARS-CoV-2. Despite robust infection of the lungs and diminishment of pulmonary cellularity, the bats showed no overt signs of disease and cleared the infection after two weeks. Despite clearance of infection, only low-titer antibody responses occurred and only a single bat made neutralizing antibody. Assessment of the CD4 + helper T cell response showed that activated cells expressed the regulatory T cell cytokines IL-10 and TGFβ that may have tempered pulmonary inflammation.

SARS-CoV-2 humoral and cellular immunity following different combinations of vaccination and breakthrough infection

The elicited anti-SARS-CoV-2 immunity is becoming increasingly complex with individuals receiving a different number of vaccine doses paired with or without recovery from breakthrough infections with different variants. Here we analyze the immunity of individuals that initially received two doses of mRNA vaccine and either received a booster vaccination, recovered from a breakthrough infection, or both. Our data suggest that two vaccine doses and delta breakthrough infection or three vaccine doses and optionally omicron or delta infection provide better B cell immunity than the initial two doses of mRNA vaccine with or without alpha breakthrough infection. A particularly potent B cell response against the currently circulating omicron variant (B. 1.1.529) was observed for thrice vaccinated individuals with omicron breakthrough infection; a 46-fold increase in plasma neutralization compared to two vaccine doses (p < 0.0001). The T cell response after two vaccine doses is not significantly influenced by additional antigen exposures. Of note, individuals with hybrid immunity show better correlated adaptive immune responses compared to those only vaccinated. Taken together, our data provide a detailed insight into SARS-CoV-2 immunity following different antigen exposure scenarios.

Efficient recall of SARS-CoV-2 variant-reactive B cells and T responses in the elderly upon heterologous mRNA vaccines as boosters

Waning antibody levels against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and the emergence of variants of concern highlight the need for booster vaccinations. This is particularly important for the elderly population, who are at a higher risk of developing severe coronavirus disease 2019 (COVID-19) disease. While studies have shown increased antibody responses following booster vaccination, understanding the changes in T and B cell compartments induced by a third vaccine dose remains limited. We analyzed the humoral and cellular responses in subjects who received either a homologous messenger RNA(mRNA) booster vaccine (BNT162b2 + BNT162b2 + BNT162b2; ''BBB") or a heterologous mRNA booster vaccine (BNT162b2 + BNT162b2 + mRNA-1273; ''BBM") at Day 0 (prebooster), Day 7, and Day 28 (postbooster). Compared with BBB, elderly individuals (≥60 years old) who received the BBM vaccination regimen display higher levels of neutralizing antibodies against the Wuhan and Delta strains along with a higher boost in immunoglobulin G memory B cells, particularly against the Omicron variant. Circulating T helper type 1(Th1), Th2, Th17, and T follicular helper responses were also increased in elderly individuals given the BBM regimen. While mRNA vaccines increase antibody, T cell, and B cell responses against SARS-CoV-2 1 month after receiving the third dose booster, the efficacy of the booster vaccine strategies may vary depending on age group and regimen combination.

Memory B Cells and Memory T Cells Induced by SARS-CoV-2 Booster Vaccination or Infection Show Different Dynamics and Responsiveness to the Omicron Variant

Although the immunological memory produced by BNT162b2 vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been well studied and established, further information using different racial cohorts is necessary to understand the overall immunological response to vaccination. We evaluated memory B and T cell responses to the severe acute respiratory syndrome coronavirus 2 spike protein before and after the third booster using a Japanese cohort. Although the Ab titer against the spike receptor-binding domain (RBD) decreased significantly 8 mo after the second vaccination, the number of memory B cells continued to increase, whereas the number of memory T cells decreased slowly. Memory B and T cells from unvaccinated infected patients showed similar kinetics. After the third vaccination, the Ab titer increased to the level of the second vaccination, and memory B cells increased at significantly higher levels before the booster, whereas memory T cells recovered close to the second vaccination levels. In memory T cells, the frequency of CXCR5+CXCR3+CCR6- circulating follicular Th1 was positively correlated with RBD-specific Ab-secreting B cells. For the response to variant RBDs, although 60-80% of memory B cells could bind to the omicron RBD, their avidity was low, whereas memory T cells show an equal response to the omicron spike. Thus, the persistent presence of memory B and T cells will quickly upregulate Ab production and T cell responses after omicron strain infection, which prevents severe illness and death due to coronavirus disease 2019.

CXCL12 and CXCL13 Cytokine Serum Levels Are Associated with the Magnitude and the Quality of SARS-CoV-2 Humoral Responses

A better understanding of the immunological markers associated with long-lasting immune responses to SARS-CoV-2 infection is of paramount importance. In the present study, we characterized SARS-CoV-2-specific humoral responses in hospitalized (ICU and non-ICU) and non-hospitalized individuals at six months post-onset of symptoms (POS) (N = 95). We showed that the proportion of individuals with detectable anti-SARS-CoV-2 IgG or neutralizing (NAb) responses and the titers of antibodies were significantly reduced in non-hospitalized individuals, compared to ICU- or non-ICU-hospitalized individuals at 6 months POS. Interestingly, SARS-CoV-2-specific memory B cells persist at 6 months POS in both ICU and non-ICU patients and were enriched in cells harboring an activated and/or exhausted phenotype. The frequency/phenotype of SARS-CoV-2-specific memory B cells and the magnitude of IgG or NAb responses at 6 months POS correlated with the serum immune signature detected at patient admission. In particular, the serum levels of CXCL13, IL-1RA, and G-CSF directly correlated with the frequency of Spike-specific B cells and the magnitude of Spike-specific IgG or NAb, while the serum levels of CXCL12 showed an antagonizing effect. Our results indicate that the balance between CXCL12 and CXCL13 is an early marker associated with the magnitude and the quality of the SARS-CoV-2 humoral memory.

Adaptive immunity to SARS-CoV-2 infection: A systematic review

BACKGROUND

There is evidence that the adaptive or acquired immune system is one of the crucial variables in differentiating the course of coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). This work aimed to analyze the immunopathological aspects of adaptive immunity that are involved in the progression of this disease.

METHODS

This is a systematic review based on articles that included experimental evidence from in vitro assays, cohort studies, reviews, cross-sectional and case-control studies from PubMed, SciELO, MEDLINE, and Lilacs databases in English, Portuguese, or Spanish between January 2020 and July 2022.

RESULTS

Fifty-six articles were finalized for this review. CD4+ T cells were the most resolutive in the health-disease process compared with B cells and CD8+ T lymphocytes. The predominant subpopulations of T helper lymphocytes (Th) in critically ill patients are Th1, Th2, Th17 (without their main characteristics) and regulatory T cells (Treg), while in mild cases there is an influx of Th1, Th2, Th17 and follicular T helper cells (Tfh). These cells are responsible for the secretion of cytokines, including interleukin (IL) - 6, IL-4, IL-10, IL-7, IL-22, IL-21, IL-15, IL-1α, IL-23, IL-5, IL-13, IL-2, IL-17, tumor necrosis factor alpha (TNF-α), CXC motivating ligand (CXCL) 8, CXCL9 and tumor growth factor beta (TGF-β), with the abovementioned first 8 inflammatory mediators related to clinical benefits, while the others to a poor prognosis. Some CD8+ T lymphocyte markers are associated with the severity of the disease, such as human leukocyte antigen (HLA-DR) and programmed cell death protein 1 (PD-1). Among the antibodies produced by SARS-CoV-2, Immunoglobulin (Ig) A stood out due to its potent release associated with a more severe clinical form.

CONCLUSIONS

It is concluded that through this study it is possible to have a brief overview of the main immunological biomarkers and their function during SARS-CoV-2 infection in particular cell types. In critically ill individuals, adaptive immunity is varied, aberrantly compromised, and late. In particular, the T-cell response is also an essential and necessary component in immunological memory and therefore should be addressed in vaccine formulation strategies.

Comparison of Homologous and Heterologous Booster SARS-CoV-2 Vaccination in Autoimmune Rheumatic and Musculoskeletal Patients

Vaccination against SARS-CoV-2 to prevent COVID-19 is highly recommended for immunocompromised patients with autoimmune rheumatic and musculoskeletal diseases (aiRMDs). Little is known about the effect of booster vaccination or infection followed by previously completed two-dose vaccination in aiRMDs. We determined neutralizing anti-SARS-CoV-2 antibody levels and applied flow cytometric immunophenotyping to quantify the SARS-CoV-2 reactive B- and T-cell mediated immunity in aiRMDs receiving homologous or heterologous boosters or acquired infection following vaccination. Patients receiving a heterologous booster had a higher proportion of IgM+ SARS-CoV-2 S+ CD19+CD27+ peripheral memory B-cells in comparison to those who acquired infection. Biologic therapy decreased the number of S+CD19+; S+CD19+CD27+IgG+; and S+CD19+CD27+IgM+ B-cells. The response rate to a booster event in cellular immunity was the highest in the S-, M-, and N-reactive CD4+CD40L+ T-cell subset. Patients with a disease duration of more than 10 years had higher proportions of CD8+TNF-α+ and CD8+IFN-γ+ T-cells in comparison to patients who were diagnosed less than 10 years ago. We detected neutralizing antibodies, S+ reactive peripheral memory B-cells, and five S-, M-, and N-reactive T-cells subsets in our patient cohort showing the importance of booster events. Biologic therapy and <10 years disease duration may confound anti-SARS-CoV-2 specific immunity in aiRMDs.

The need for more holistic immune profiling in next-generation SARS-CoV-2 vaccine trials

First-generation anit-SARS-CoV-2 vaccines were highly successful. They rapidly met an unforeseen emergency need, saved millions of lives, and simultaneously eased the burden on healthcare systems worldwide. The first-generation vaccines, however, focused too narrowly on antibody-based immunity as the sole marker of vaccine trial success, resulting in large knowledge gaps about waning vaccine protection, lack of vaccine robustness to viral mutation, and lack of efficacy in immunocompromised populations. Detailed reviews of first-generation vaccines, including their mode of action and geographical distribution, have been published elsewhere. Second-generation clinical trials must address these gaps by evaluating a broader range of immune markers, including those representing cell-mediated immunity, to ensure the most protective and long-lasting vaccines are brought to market.

Single-cell analysis of the adaptive immune response to SARS-CoV-2 infection and vaccination

Amid the ongoing Coronavirus Disease 2019 (COVID-19) pandemic, vaccination and early therapeutic interventions are the most effective means to combat and control the severity of the disease. Host immune responses to SARS-CoV-2 and its variants, particularly adaptive immune responses, should be fully understood to develop improved strategies to implement these measures. Single-cell multi-omic technologies, including flow cytometry, single-cell transcriptomics, and single-cell T-cell receptor (TCR) and B-cell receptor (BCR) profiling, offer a better solution to examine the protective or pathological immune responses and molecular mechanisms associated with SARS-CoV-2 infection, thus providing crucial support for the development of vaccines and therapeutics for COVID-19. Recent reviews have revealed the overall immune landscape of natural SARS-CoV-2 infection, and this review will focus on adaptive immune responses (including T cells and B cells) to SARS-CoV-2 revealed by single-cell multi-omics technologies. In addition, we explore how the single-cell analyses disclose the critical components of immune protection and pathogenesis during SARS-CoV-2 infection through the comparison between the adaptive immune responses induced by natural infection and by vaccination.

Recovering or Persisting: The Immunopathological Features of SARS-CoV-2 Infection in Children

Background. The profile of cellular immunological responses of children across the spectrum of COVID-19, ranging from acute SARS-CoV-2 infection to full recovery or Long COVID, has not yet been fully investigated. Methods. We examined and compared cytokines in sera and cell subsets in peripheral blood mononuclear cells (B and regulatory T lymphocytes) collected from four distinct groups of children, distributed as follows: younger than 18 years of age with either acute SARS-CoV-2 infection (n = 49); fully recovered from COVID-19 (n = 32); with persistent symptoms (Long COVID, n = 51); and healthy controls (n = 9). Results. In the later stages after SARS-CoV-2 infection, the cohorts of children, both with recovered and persistent symptoms, showed skewed T and B subsets, with remarkable differences when compared with children at the onset of the infection and with controls. The frequencies of IgD+CD27− naïve B cells, IgD+IgM+ and CD27−IgM+CD38dim B cells were higher in children with recent infection than in those with an older history of disease (p < 0.0001 for all); similarly, the total and natural Tregs compartments were more represented in children at onset when compared with Long COVID (p < 0.0001 and p = 0.0005, respectively). Despite the heterogeneity, partially due to age, sex and infection incidence, the susceptibility of certain children to develop persistent symptoms after infection appeared to be associated with the imbalance of the adaptive immune response. Following up and comparing recovered versus Long COVID patients, we analyzed the role of circulating naïve and switched B and regulatory T lymphocytes in counteracting the evolution of the symptomatology emerged, finding an interesting correlation between the amount and ability to reconstitute the natural Tregs component with the persistence of symptoms (linear regression, p = 0.0026). Conclusions. In this study, we suggest that children affected by Long COVID may have a compromised ability to switch from the innate to the adaptive immune response, as supported by our data showing a contraction of naïve and switched B cell compartment and an unstable balance of regulatory T lymphocytes occurring in these children. However, further prospective immunological studies are needed to better clarify which factors (epigenetic, diet, environment, etc.) are involved in the impairment of the immunological mechanisms in the Long COVID patients.

A Complementary Union of SARS-CoV2 Natural and Vaccine Induced Immune Responses

Our understanding of the immune responses that follow SARS-CoV-2 infection and vaccination has progressed considerably since the COVID-19 pandemic was first declared on the 11th of March in 2020. Recovery from infection is associated with the development of protective immune responses, although over time these become less effective against new emerging SARS-CoV-2 variants. Consequently, reinfection with SARS-CoV-2 variants is not infrequent and has contributed to the ongoing pandemic. COVID-19 vaccines have had a tremendous impact on reducing infection and particularly the number of deaths associated with SARS-CoV-2 infection. However, waning of vaccine induced immunity plus the emergence of new variants has necessitated the use of boosters to maintain the benefits of vaccination in reducing COVID-19 associated deaths. Boosting is also beneficial for individuals who have recovered from COVID-19 and developed natural immunity, also enhancing responses immune responses to SARS-CoV-2 variants. This review summarizes our understanding of the immune responses that follow SARS-CoV-2 infection and vaccination, the risks of reinfection with emerging variants and the very important protective role vaccine boosting plays in both vaccinated and previously infected individuals.

Persistent Maintenance of Intermediate Memory B Cells Following SARS-CoV-2 Infection and Vaccination Recall Response

Robust population-wide immunity will help to curb the SARS-CoV-2 pandemics. To maintain the immunity at protective levels, the quality and persistence of the immune response elicited by infection or vaccination must be determined. We analyzed the dynamics of B cell response during 12 months following SARS-CoV-2 infection on an individual level. In contrast to antibodies, memory B cells specific for the spike (S) protein persisted at high levels throughout the period. These cells efficiently secreted neutralizing antibodies and correlated with IFN-γ-secreting CD4⁺ T cells. Interestingly, the CD27⁻CD21⁺ intermediate memory B cell phenotype was associated with high B cell receptor avidity and the production of neutralizing antibodies. Vaccination of previously infected individuals triggered a recall response enhancing neutralizing antibody and memory B cell levels. Collectively, our findings provide a detailed insight into the longevity of SARS-CoV-2-infection-induced B cell immunity and highlight the importance of vaccination among previously infected.

IMPORTANCE To efficiently maintain immunity against SARS-CoV-2 infection, we must first determine the durability of the immune response following infection or vaccination. Here, we demonstrated that, unlike antibodies, virus-specific memory B cells persist at high levels for at least 12 months postinfection and successfully respond to a secondary antigen challenge. Furthermore, we demonstrated that vaccination of previously infected individuals significantly boosters B cell immunity.

Helminth antigens differentially modulate the activation of CD4+ and CD8+ T lymphocytes of convalescent COVID-19 patients in vitro

BACKGROUND

The coronavirus disease 2019 (COVID-19) is a respiratory disease caused by SARS-CoV-2, a recently discovered strain of coronavirus. The virus has spread rapidly, causing millions of death worldwide. Contrary to the predictions, prevalence and mortality due to COVID-19 have remained moderate on the African continent. Several factors, including age, genetics, vaccines, and co-infections, might impact the course of the pandemic in Africa. Helminths are highly endemic in Sub-Saharan Africa and are renowned for their ability to evade, skew, and suppress human immune responses through various immune-modulatory mechanisms. Such effects will likely impact SARS-CoV-2 transmission and disease progression.

METHODS

Here, we analyzed in vitro the impact of antigen extracts from three major helminth parasites, including Onchocerca volvulus, Brugia malayi, and Ascaris lumbricoides, on the immune reactivity to SARS-CoV-2 peptides in COVID-19 patients. Activation of CD4⁺ and CD8⁺ T cells was investigated using flow cytometry to monitor the expression of CD137 (4-1BB) and CD69. Cytokine expression, including IL-6, IL-10, IFN-γ, and TNFα, was measured by Luminex in cell culture supernatants.

RESULTS

We observed that helminth antigens significantly reduced the frequency of SARS-CoV-2-reactive CD4⁺ T helper cells. In contrast, the expression of SARS-CoV-2-reactive CD8⁺ T cells was not affected and even significantly increased when PBMCs from COVID-19 patients living in Benin, an endemic helminth country, were used. In addition, stimulation with helminth antigens was associated with increased IL-10 and a reduction of IFNγ and TNFα.

CONCLUSIONS

Our data offer a plausible explanation for the moderate incidence of COVID-19 in Africa and support the hypothesis that helper T cell-mediated immune responses to SARS-CoV-2 are mitigated in the presence of helminth antigens, while virus-specific cytotoxic T cell responses are maintained.

Anti-Spike Antibody Response to Natural Infection with SARS-CoV-2 and Its Activity against Emerging Variants

The outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has substantially affected human health globally. Spike-specific antibody response plays a major role in protection against SARS-CoV-2 infection. Here, we examined serological anti-spike antibody and memory B cell responses in adults with acute SARS-CoV-2 infection. Twenty-five adult patients were enrolled between January and September 2020, and 21 (84%) had a detectable spike-binding antibody response in serum on day 21 ± 8 (6 to 33) after the onset of illness. Among those with positive spike-binding antibody response, 19 (90%) had a positive hemagglutination titer and 15 (71%) had angiotensin-converting enzyme 2 (ACE2)-blocking serological activities. Follow-up serum samples collected 11 ± 1 (7 to 15) months after infection exhibited an average of 2.6 ± 1.0 (1.0 to 3.5)-fold reduction in the spike-binding antibody response. Moreover, convalescent and follow-up serum samples showed 83 ± 82 (15 to 306)- and 165 ± 167 (12 to 456)-fold reductions in the neutralization activity against the Omicron variant, respectively. Upon acute infection, spike-specific memory B cell responses were elicited, with an average frequency of 1.3% ± 1.2% of peripheral B cells on day 19 ± 7 (6 to 33) after the onset of illness. IgM memory B cells were predominantly induced. Patients with fever and pneumonia showed significantly stronger spike-binding, ACE2-blocking antibody, and memory B cell responses. In conclusion, spike-specific antibody response elicited upon acute SARS-CoV-2 infection may wane over time and be compromised by the emergence of viral variants.

IMPORTANCE As spike protein-specific antibody responses play a major role in protection against SARS-CoV-2, we examined spike-binding and ACE2-blocking antibody responses in SARS-CoV-2 infection at different time points. We found robust responses following acute infection, which waned approximately 11 months after infection. Patients with fever and pneumonia showed significantly stronger spike-binding, ACE2-blocking antibody, and memory B cell responses. In particular, spike-specific antibody response in the convalescent and follow-up serum samples was substantially affected by emerging variants, especially Beta and Omicron variants. These results warrant continued surveillance of spike-specific antibody responses to natural infections and highlight the importance of maintaining functional anti-spike antibodies through immunization.

Heterologous prime-boost strategies for COVID-19 vaccines

BACKGROUND/OBJECTIVE

Heterologous prime-boost doses of COVID-19 vaccines ('mix-and-match' approach) are being studied to test for the effectiveness of Oxford (AZD1222), Pfizer (BNT162b2), Moderna (mRNA-1273) and Novavax (NVX-CoV2373) vaccines for COVID in 'Com-Cov2 trial' in UK, and that of Oxford and Pfizer vaccines in 'CombivacS trial' in Spain. Later, other heterologous combinations of CoronaVac (DB15806), Janssen (JNJ-78436735), CanSino (AD5-nCOV) and other were also being trialled to explore their effectiveness. Previously, such a strategy was deployed for HIV, Ebola virus, malaria, tuberculosis, influenza and hepatitis B to develop the artificial acquired active immunity. The present review explores the science behind such an approach for candidate COVID-19 vaccines developed using 11 different platforms approved by the World Health Organization.

METHODS

The candidate vaccines' pharmaceutical parameters (e.g. platforms, number needed to vaccinate and intervals, adjuvanted status, excipients and preservatives added, efficacy and effectiveness, vaccine adverse events, and boosters), and clinical aspects must be analysed for the mix-and-match approach. Results prime-boost trials showed safety, effectiveness, higher systemic reactogenicity, well tolerability with improved immunogenicity, and flexibility profiles for future vaccinations, especially during acute and global shortages, compared to the homologous counterparts.

CONCLUSION

Still, large controlled trials are warranted to address challenging variants of concerns including Omicron and other, and to generalize the effectiveness of the approach in regular as well as emergency use during vaccine scarcity.

The COVID-19 pandemic in the African continent

In December 2019, a new coronavirus, severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and associated disease, coronavirus disease 2019 (COVID-19), was identified in China. This virus spread quickly and in March, 2020, it was declared a pandemic. Scientists predicted the worst scenario to occur in Africa since it was the least developed of the continents in terms of human development index, lagged behind others in achievement of the United Nations sustainable development goals (SDGs), has inadequate resources for provision of social services, and has many fragile states. In addition, there were relatively few research reporting findings on COVID-19 in Africa. On the contrary, the more developed countries reported higher disease incidences and mortality rates. However, for Africa, the earlier predictions and modelling into COVID-19 incidence and mortality did not fit into the reality. Therefore, the main objective of this forum is to bring together infectious diseases and public health experts to give an overview of COVID-19 in Africa and share their thoughts and opinions on why Africa behaved the way it did. Furthermore, the experts highlight what needs to be done to support Africa to consolidate the status quo and overcome the negative effects of COVID-19 so as to accelerate attainment of the SDGs.

Chronic Inflammation Might Protect Hemodialysis Patients From Severe COVID-19

Hemodialysis patients (HD) are expected to have excess mortality in coronavirus disease 2019 (COVID-19). This was challenged by a recent study reporting HD patients to have comparable mortality and less ICU admissions when hospitalized with COVID-19. An altered immune system due to chronic inflammation might protect HD-patients from severe COVID-19. Therefore, we aimed to describe the peripheral blood immune phenotype in HD-patients and respective controls with COVID-19.

Robust and Functional Immune Memory Up to 9 Months After SARS-CoV-2 Infection: A Southeast Asian Longitudinal Cohort

The duration of humoral and cellular immune memory following SARS-CoV-2 infection in populations in least developed countries remains understudied but is key to overcome the current SARS-CoV-2 pandemic. Sixty-four Cambodian individuals with laboratory-confirmed infection with asymptomatic or mild/moderate clinical presentation were evaluated for Spike (S)-binding and neutralizing antibodies and antibody effector functions during acute phase of infection and at 6-9 months follow-up. Antigen-specific B cells, CD4⁺ and CD8⁺ T cells were characterized, and T cells were interrogated for functionality at late convalescence. Anti-S antibody titers decreased over time, but effector functions mediated by S-specific antibodies remained stable. S- and nucleocapsid (N)-specific B cells could be detected in late convalescence in the activated memory B cell compartment and are mostly IgG⁺. CD4⁺ and CD8⁺ T cell immune memory was maintained to S and membrane (M) protein. Asymptomatic infection resulted in decreased antibody-dependent cellular cytotoxicity (ADCC) and frequency of SARS-CoV-2-specific CD4⁺ T cells at late convalescence. Whereas anti-S antibodies correlated with S-specific B cells, there was no correlation between T cell response and humoral immune memory. Hence, all aspects of a protective immune response are maintained up to nine months after SARS-CoV-2 infection and in the absence of re-infection.

Immune response to the third COVID-19 vaccine dose is related to lymphocyte count in multiple sclerosis patients treated with fingolimod

Background

The majority of multiple sclerosis [MS] patients treated with fingolimod fail to develop a protective level of IgG humoral and adaptive cellular immune responses following full BNT162b2 SARS-CoV-2 vaccination.

Objective

To compare the efficacy of the third COVID-19 vaccine dose in vaccine non-responders fingolimod-treated MS patients.

Study design

This is a prospective 3-month, single-center, randomized clinical trial.

Methods

Twenty relapsing MS patients who had been on fingolimod therapy ≥ 12 months and failed to develop humoral IgG immune response to 2-dose Pfizer BNT162b2 COVID-19 vaccination were randomized into two groups: fingolimod-continuation group and fingolimod-discontinuation group. Humoral and memory cellular immune responses were assessed within 1 and 3 months following the third Pfizer BNT162b2 vaccine dose and compared between the groups.

Results

A higher rate of patients in the fingolimod-discontinuation group [n = 8/10] compared to fingolimod-continuation group [n = 2/10] developed positive SARS-COV-2 IgG. Median IgG titer 1 month following the third dose was 202.3 BAU/ml vs. 26.4 BAU/ml, respectively, p = 0.022. The development of IgG humoral response correlated with absolute lymphocyte count. Specific SARS-COV-2 memory B cell and T cell immune responses were not detected in both groups, either at 1 month or 3 months following the third COVID-19 vaccine dose.

Conclusions

Short period of fingolimod treatment discontinuation was associated with the development of humoral protection but not with adaptive cellular immunity.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00415-022-11030-0.

Cross-Neutralizing Breadth and Longevity Against SARS-CoV-2 Variants After Infections

Background

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is the virus responsible for the Coronavirus Disease 2019 (COVID-19) pandemic. The emergence of variants of concern (VOCs) has become one of the most pressing issues in public health. To control VOCs, it is important to know which COVID-19 convalescent sera have cross-neutralizing activity against VOCs and how long the sera maintain this protective activity.

Methods

Sera of patients infected with SARS-CoV-2 from March 2020 to January 2021 and admitted to Hyogo Prefectural Kakogawa Medical Center were selected. Blood was drawn from patients at 1-3, 3-6, and 6-8 months post onset. Then, a virus neutralization assay against SARS-CoV-2 variants (D614G mutation as conventional strain; B.1.1.7, P.1, and B.1.351 as VOCs) was performed using authentic viruses.

Results

We assessed 97 sera from 42 patients. Sera from 28 patients showed neutralizing activity that was sustained for 3-8 months post onset. The neutralizing antibody titer against D614G significantly decreased in sera of 6-8 months post onset compared to those of 1-3 months post onset. However, the neutralizing antibody titers against the three VOCs were not significantly different among 1-3, 3-6, and 6-8 months post onset.

Discussion

Our results indicate that neutralizing antibodies that recognize the common epitope for several variants may be maintained for a long time, while neutralizing antibodies having specific epitopes for a variant, produced in large quantities immediately after infection, may decrease quite rapidly.

A chitosan-mediated inhalable nanovaccine against SARS-CoV-2

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), with several antigenic variants, has grown into a global challenge, and the rapid establishment of an immune barrier is crucial to achieving long-term control of the virus. This has led to a great demand for easy preparation and scalable vaccines, especially in low-income countries. Here, we present an inhalable nanovaccine comprising chitosan and SARS-CoV-2 spike protein. The chitosan-mediated nanovaccine enabled a strong spike-specific antibody immune response and augmented local mucosal immunity in bronchoalveolar lavage and lungs, which might be capable of protecting the host from infection without systemic toxicity. In addition, the enhanced adaptive immunity stimulated by chitosan showed potential protection against SARS-CoV-2. Furthermore, inhalation of the nanovaccine induced a comparable antibody response compared to intramuscular injection. This inhalable nanovaccine against SARS-CoV-2 offers a convenient and compliant strategy to reduce the use of needles and the need for medical staff.

ELECTRONIC SUPPLEMENTARY MATERIAL

Supplementary material (the immune activation of CS-mediated nanovacccine on BMDCs, cell viability, immune responses in lungs and BALF, serum chemistry and H&E histopathological analysis.) is available in the online version of this article at 10.1007/s12274-021-4012-9.

Long-term perturbation of the peripheral immune system months after SARS-CoV-2 infection

BACKGROUND

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a highly infectious respiratory virus which is responsible for the coronavirus disease 2019 (COVID-19) pandemic. It is increasingly clear that recovered individuals, even those who had mild COVID-19, can suffer from persistent symptoms for many months after infection, a condition referred to as "long COVID", post-acute sequelae of COVID-19 (PASC), post-acute COVID-19 syndrome, or post COVID-19 condition. However, despite the plethora of research on COVID-19, relatively little is known about the molecular underpinnings of these long-term effects.

METHODS

We have undertaken an integrated analysis of immune responses in blood at a transcriptional, cellular, and serological level at 12, 16, and 24 weeks post-infection (wpi) in 69 patients recovering from mild, moderate, severe, or critical COVID-19 in comparison to healthy uninfected controls. Twenty-one of these patients were referred to a long COVID clinic and > 50% reported ongoing symptoms more than 6 months post-infection.

RESULTS

Anti-Spike and anti-RBD IgG responses were largely stable up to 24 wpi and correlated with disease severity. Deep immunophenotyping revealed significant differences in multiple innate (NK cells, LD neutrophils, CXCR3+ monocytes) and adaptive immune populations (T helper, T follicular helper, and regulatory T cells) in convalescent individuals compared to healthy controls, which were most strongly evident at 12 and 16 wpi. RNA sequencing revealed significant perturbations to gene expression in COVID-19 convalescents until at least 6 months post-infection. We also uncovered significant differences in the transcriptome at 24 wpi of convalescents who were referred to a long COVID clinic compared to those who were not.

CONCLUSIONS

Variation in the rate of recovery from infection at a cellular and transcriptional level may explain the persistence of symptoms associated with long COVID in some individuals.

Maintenance of broad neutralising antibodies and memory B cells 12 months post-infection is predicted by SARS-CoV-2 specific CD4+ T cell responses

Understanding the long-term maintenance of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) immunity is critical for predicting protection against reinfection. In an age- and gender-matched cohort of 24 participants, the association of disease severity and early immune responses on the maintenance of humoral immunity 12 months post-infection is examined. All severely affected participants maintain a stable subset of SARS-CoV-2 receptor-binding domain (RBD)-specific memory B cells (MBCs) and good neutralizing antibody breadth against the majority of the variants of concern, including the Delta variant. Modeling these immune responses against vaccine efficacy data indicate a 45%–76% protection against symptomatic infection (variant dependent). Overall, these findings indicate durable humoral responses in most participants after infection, reasonable protection against reinfection, and implicate baseline antigen-specific CD4+ T cell responses as a predictor of maintenance of antibody neutralization breadth and RBD-specific MBC levels at 12 months post-infection.

An exploratory review of Potential Adjunct Therapies for the Treatment of Coronavirus Infections

Objective

The purpose of this exploratory review c, including vitamin D, zinc, vitamin A, elderberry (S nigra), garlic (A sativum), licorice (G glabra), stinging nettle (U dioica), N-acetylcysteine, quercetin and selenium as potential adjunct therapies for the treatment of coronavirus infections.

Methods

A search of PubMed was performed for articles published from 2005 to 2021. Key words searched were zinc, vitamin A, vitamin D, Sambucus nigra, Allium sativum, Glycyrrhiza glabra, Urtica dioica, N-Acetylcysteine, quercetin, selenium and coronavirus.

Results

There were 47 articles selected for this review. Findings included that vitamin D, zinc, vitamin A, S nigra, A sativum, G glabra, U dioica, N-acetylcysteine, quercetin and selenium have been shown to produce anti-inflammatory, immunostimulatory or antiviral effects that may enhance the actions of standard therapeutics for the treatment of CoV infections. We found only research articles related to the effects of vitamin D, zinc, G glabra, quercetin and selenium against COVID-19.

Conclusion

We identified non-pharmaceutical supplements (Vitamin D, zinc, vitamin A, S nigra, A sativum, G glabra and U dioica) which may have potential to provide support for those with coronavirus infections. However, rigorous clinical studies need to be performed before any clinical recommendations can be made at this time.

Role of multiple factors likely contributing to severity-mortality of COVID-19

COVID-19 stalled the world in 2020 and continues to be the greatest health crisis of this generation. While the apparent case fatality rates across fluctuates around ~2% globally, associated mortality/death rate (deaths per million population) varies distinctly across regions from the global average of ~600 per million population. Heterogeneous factors have been linked with COVID-19 associated mortalities and these include age, share of geriatric population, comorbidities, trained immunity and climatic conditions. Apart from direct or indirect role of endemic diseases, dietary factors and host immunity in regulating COVID-19 severity, human behaviour will inevitably control outcome of this pandemic. Comprehensive understanding of these factors will have a bearing on management of future health crises.

COVID-19 Risk Assessment for the Tokyo Olympic Games

Introduction: As of June 7, 2021, the outbreak of Coronavirus Disease 2019 (COVID-19) has spread to more than 200 countries. The global number of reported cases is more than 172.9 million, with more than 3.7 million deaths, and the number of infected individuals is still growing rapidly. Consequently, events and activities around the world were canceled or postponed, and the preparation for sporting events were greatly challenged. Under such circumstances, about 11,000 athletes from ~206 countries are arriving in Tokyo for the 32nd Summer Olympic Games. Therefore, it is urgently necessary to assess the occurrence and spread risk of COVID-19 for the Games. Objectives: To explore effective prevention and control measures for COVID-19 in large international events through simulations of different interventions according to risk assessment. Methods: We used a random model to calculate the number of initial infected patients and used Poisson distribution to determine the number of initial infected patients based on the number of countries involved. Furthermore, to simulate the COVID-19 transmission, the susceptible-exposed-symptomatic-asymptomatic-recovered-hospitalized (SEIARH) model was established based on the susceptible-exposed-infectious-recovered (SEIR) mathematical model of epidemic diseases. According to risk assessment indicators produced by different scenarios of the simulated interventions, the risk of COVID-19 transmission in Tokyo Olympic Games was assessed. Results: The current COVID-19 prevention measures proposed by the Japan Olympic Committee need to be enhanced. And large-scale vaccination will effectively control the spread of COVID-19. When the protective efficacy of vaccines is 78.1% or 89.8%, and if the vaccination rate of athletes reaches 80%, an epidemic prevention barrier can be established.

Immunity Profiling of COVID-19 Infection, Dynamic Variations of Lymphocyte Subsets, a Comparative Analysis on Four Different Groups

Background: A novel coronavirus (SARS-CoV-2)-induced pneumonia (COVID-19) emerged in December 2019 in China, spreading worldwide. The aim of the present investigation was to evaluate the immunological response and the clinical subset of peripheral lymphocyte subset alteration in COVID-19 infection. Methods: the study was conducted on four different clinical groups (n = 4; total n = 138). Each individual was assigned to different groups based on specific criteria evaluated at the admission such as fever, dyspnea, arterial blood gas analysis (ABG), oral-nasopharyngeal swab/RT-PCR, and thoracic CT-scan. Treatment was performed only after blood samples were collected from each patient (PP and PP) at day 1. The blood samples were analyzed and tested the same day (CBC and Flowcytometry). The positive–positive group (PP n = 45; F = 18/ M = 27; median age = 62.33), comprised individuals affected by COVID-19 who showed fever, dyspnea (ABG = pO2 < 60), confirmed positive by oral-nasopharyngeal swab/RT-PCR and with CT-scan showing ground-glass opacities. The negative–positive (NP; n = 37; F = 11/M = 26; median age = 75.94) or “COVID-like” group comprised individuals with fever and dyspnea (ABG = pO2 < 60), who tested negative to nasopharyngeal swab/RT-PCR, with CT-scans showing ground-glass opacities in the lungs. The negative–affected group (NA; n = 40; F = 14/M = 26; median age = 58.5) included individuals negative to COVID-19 (RT-PCR) but affected by different chronic respiratory diseases (the CT-scans didn’t show ground-glass opacities). Finally, the negative–negative group (NN; n = 16; F = 14/M = 2) included healthy patients (NN; n = 16; median age = 42.62). Data and findings were collected and compared. Results: Lymphocytes (%) cells showed a decline in COVID-19 patients. The subsets showed a significant association with the inflammatory status in COVID-19, especially with regard to increased neutrophils, T-killer, T-active, T-suppressor, and T-CD8+CD38+ in individuals belong to the either COVID-19 and Covid-like NP group. Conclusions: Peripheral lymphocyte subset alteration was associated with the clinical characteristics and progression of COVID-19. The level of sub-set cells T-lymphocytes (either high or low) and B-lymphocytes could be used as an independent predictor for COVID-19 severity and treatment efficacy.

COVID-19 Vaccines: Current Conditions and Future Prospects

Simple Summary

The coronavirus disease 2019 (COVID-19) pandemic, caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was first encountered in December of 2019 in Wuhan, China. As of now, there have been over 200 million infections and 4 million deaths attributed to the virus. Due to this, it has been a priority to find an effective preventative measure, and numerous vaccines have been developed. Although the developed vaccines share the target of blocking viral entry by the spike protein, their pharmacology and efficacy differs. As such, the mechanism of action and the elicited immune response of the most common COVID-19 vaccines have been compared to help determine which vaccine is most efficacious and is best suited to prevent reinfection and address viral mutations.

Abstract

It has been over a year since SARS-CoV-2 was first reported in December of 2019 in Wuhan, China. To curb the spread of the virus, many therapies and cures have been tested and developed, most notably mRNA and DNA vaccines. Federal health agencies (CDC, FDA) have approved emergency usage of these S gene-based vaccines with the intention of minimizing any further loss of lives and infections. It is crucial to assess which vaccines are the most efficacious by examining their effects on the immune system, and by providing considerations for new technological vaccine strategies in the future. This paper provides an overview of the current SARS-CoV-2 vaccines with their mechanisms of action, current technologies utilized in manufacturing of the vaccines, and limitations in this new field with emerging data. Although the most popular COVID-19 vaccines have been proven effective, time will be the main factor in dictating which vaccine will be able to best address mutations and future infection.

Advances in understanding the formation and fate of B-cell memory in response to immunization or infection

Immunological memory has the potential to provide lifelong protection against recurrent infections. As such, it has been crucial to the success of vaccines. Yet, the recent pandemic has illuminated key gaps in our knowledge related to the factors influencing effective memory formation and the inability to predict the longevity of immune protection. In recent decades, researchers have acquired a number of novel and powerful tools with which to study the factors underpinning humoral memory. These tools have been used to study the B-cell fate decisions that occur within the germinal centre (GC), a site where responding B cells undergo affinity maturation and are one of the major routes for memory B cell and high-affinity long-lived plasma cell formation. The advent of single-cell sequencing technology has provided an enhanced resolution for studying fate decisions within the GC and cutting-edge techniques have enabled researchers to model this reaction with more accuracy both in vitro and in silico. Moreover, modern approaches to studying memory B cells have allowed us to gain a better appreciation for the heterogeneity and adaptability of this vital class of B cells. Together, these studies have facilitated important breakthroughs in our understanding of how these systems operate to ensure a successful immune response. In this review, we describe recent advances in the field of GC and memory B-cell biology in order to provide insight into how humoral memory is formed, as well as the potential for generating lasting immunity to novel pathogens such as severe acute respiratory syndrome coronavirus 2.

Interleukin-21 in Viral Infections

Interleukin (IL)-21 is a cytokine that affects the differentiation and function of lymphoid and myeloid cells and regulates both innate and adaptive immune responses. In addition to regulating the immune response to tumor and viral infections, IL-21 also has a profound effect on the development of autoimmune and inflammatory diseases. IL-21 is produced mainly from CD4⁺ T cells-in particular, follicular helper T (Tfh) cells-which have a great influence on the regulation of antibody production. It is also an important cytokine for the activation of CD8⁺ T cells, and its role in recovering the function of CD8⁺ T cells exhausted by chronic microbial infections and cancer has been clarified. Thus, IL-21 plays an extremely important role in viral infections, especially chronic viral infections. In this review, I will introduce the findings to date on how IL-21 is involved in some typical viral infections and the potential of treating viral diseases with IL-21.